Western observers of Japan have noted since antiquity how unabashed the Japanese are regarding things about the human body that Westerners are typically squeamish - at worst prudish - about.

One example is how until relatively recently in history, bathhouses in Japan were not gender discriminatory; both sexes bathed together. Another is phallic festivals in Japan where that bogeyman of traditional Western morality, the penis, is elevated to religious significance. Another is the prevalence of erotica in Japan that is fully open to public view, for example, explicit gay manga comics and doujinshi (erotic limited-edition parodies of mainstream manga), without anyone raising an eyebrow.

So it's not so surprising to see what is called a Buttocks Washing Seat on sale at a supermarket in Tokyo's Kinshicho district, depicting a decrepit trouserless old man having his ass sprayed by a woman wearing gloves and a facial expression that is probably a smile, but could be read as a longsuffering grimace as well.

On top of that, they got the spelling wrong! The product on sale here is not a seat, but a sheet: a Buttocks Washing Sheet, visible underneath the old man's ass, with the red arrow pointing to it. This is because in Japanese pronunciation, there is no distinction between the opening consonants in "see" and "she," or in "seat" and "sheet."

The red lettering on the packet under the word "Washing Seat" says "Of a size and absorbency that you can be sure will keep things around from getting dirty."

In graying Japan, it is products like the Buttocks Washing Sheet, not the disposable nappy for babies, that will see rising sales.